CAKeyframeAnimation手动进度 [英] CAKeyframeAnimation Manual Progress

问题描述

我有一个UIView，它的后备层有一个CAKeyframeAnimation，简单的直线路径设置为`path`。

我可以让动画冻结，可以这么说，并手动更改其进度？

例如：
如果路径长度为100个点，则将进度（偏移？）设置为0.45应使视图沿路径向下移动45个点。

I have a UIView whose backing layer has a CAKeyframeAnimation with a simple straight line path set as its `path`.
Can I have the animation "frozen", so to speak, and manually change its progress?
For example: If the path is 100 points in length, setting the progress (offset?) to 0.45 should have the view move 45 points down the path.

我记得通过CAMediaTiming接口看到一篇文章做了类似的事情（根据滑块上的值移动视图）但是，即使经过几个小时的搜索，我也找不到它。如果我以完全错误的方式接近这个，请告诉我。谢谢。

I remember seeing an article that did something similar (moving a view along a path based on the value from a slider) via CAMediaTiming interfaces, but I haven't been able to find it, even after a few hours of searching. If I'm approaching this in a completely wrong way, please do let me know. Thanks.

以下是一些示例代码，如果上述内容不够清晰。

Here's some sample code, if the above isn't clear enough.

- (void)setupAnimation
{

    CAKeyFrameAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"position"];

    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:_label.layer.position];
    [path addLineToPoint:(CGPoint){200, 200}];

    animation.path = path.CGPath;

    animation.duration = 1;
    animation.autoreverses = NO;
    animation.removedOnCompletion = NO;
    animation.speed = 0;

    // _label is just a UILabel in a storyboard
    [_label.layer addAnimation:animation forKey:@"LabelPathAnimation"]; 
}

- (void)sliderDidSlide:(UISlider *)slider
{
    // move _label along _animation.path for a distance that corresponds to slider.value
}

推荐答案

这是基于Jonathan的内容说，只有一点点。动画设置正确，但滑块操作方法应如下所示：

This is based on what Jonathan said, only a bit more to the point. The animation is set up correctly, but the slider action method should be as follows:

- (void)sliderDidSlide:(UISlider *)slider 
{
    // Create and configure a new CAKeyframeAnimation instance
    CAKeyframeAnimation *animation = ...;
    animation.duration = 1.0;
    animation.speed = 0;
    animation.removedOnCompletion = NO;
    animation.timeOffset = slider.value;

    // Replace the current animation with a new one having the desired timeOffset
    [_label.layer addAnimation:animation forKey:@"LabelPathAnimation"];
}

这将使标签沿动画的路径移动基于 timeOffset 。

This will make the label move along the animation's path based on timeOffset.

这篇关于CAKeyframeAnimation手动进度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！